Gas turbine engines, such as those used to drive propellers in a contra-rotating prop-fan engine, utilize compressed and expanded gasses to produce rotational motion. Such engines include a compressor section, a combustor section, and a turbine section which work cooperatively to drive a shaft. A gas flowpath passes through each of the compressor, combustor and turbine sections and fluidly connects them. Also connected to the shaft, aft of the turbine section, are multiple propellers which generate thrust.
Heated exhaust gasses from the turbine section of the gas turbine engine contact the roots of the propeller blades after being expelled from the turbine section. If the exhaust gasses do not have sufficient time to cool by mixing with ambient air prior to the gasses contacting the propeller blades, the excess heat of the gasses can wear the propeller blades significantly reducing the propeller blade life and possibly damaging the propeller blades.
In order to mitigate this effect, the prior art has relied on applying costly thermal barrier coatings to the affected areas of the blades to prevent damage from the hot exhaust gasses. Such methods are undesirable in some engines as they require periodic checks and periodic maintenance of any damaged thermal barrier coatings. Thermal barrier coating systems also include a potential risk of in-flight thermal barrier coating damage which can lead to damage to the propeller blades and affect the available thrust.